Sport involved in covering winter sports venue (3,3)
I believe the answer is:
ski run
'winter sports venue' is the definition.
'sport involved in covering' is the wordplay.
'sport' becomes 'ru' (rugby union).
'involved in' is an insertion indicator.
'covering' becomes 'skin' (skin is a kind of covering).
'ru' placed within 'skin' is 'SKI RUN'.
(Other definitions for ski run that I've seen before include "Recreational snow slope" , "Downhill course in winter" , "Boggy, swampy" , "Snow-covered slope" , "Winter sports slope" .)